mil-c-13874j 17 july 1985 superseding military...

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MIL-C-13874J17 July 1985SUPERSEDINGMIL-C-13874H30 July 1981

MILITARY SPECIFICATION

COMPRESSORS, RECIPROCATING AND ROTARY,

AIR, ELECTRIC MOTOR DRIVEN

This specification is approved for use by all Departments and Agenciesof the Department of Defense.

1. SCOPE

1.1 Scope. This specification covers electric motor-driven, garage type,recipro=g and rotary air compressors.

1.2 Classification. The compressors shall be of the following types,classes, and sizes as specified (see 6.2).

Type I -Type II -Class 1 -Class 3 -Class 4 -Size -Size -Size –

Reciprocating.Rotary.Tank-mounted.Caster mounted.Base-mounted.5 cfm at 175 psig.15 cfm at 175 psig.25 cfm at 175 psig.

2. APPLICABLE DOCUMENTS

2.1 Government documents.

2.1.1 Specifications and standards. Unless otherwise specified, thefollowing specifications and standards of the issue listed in that issue of theDepartment of Defense Index of Specifications and Standards (DoDISS) specifiedin the solicitation, form a part of this specification to the extent specified

herein.

Beneficial comments (recommendations, additions, deletions) and any pertinent

data which may be of use in improving this document should be addressed to: USA

Belvoir Research and Development Center, ATTN: STRBE-DS, Fort Belvoir, VA22060-5606 by using the self-addressed Standardization Document Improvement

Proposal (DD Form 1426) appearing at the end of this document or by letter.

FSC 4310

●DISTRIBUTION STATEMENT A. Approved for public release; distribution isunlimited.

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MIL-C-13874J

SPECIFICATIONS

FEDERAL

w-C-586

CC-M-1807

FF-C-88

GG-G-91

WW-C-566

MILITARY

MIL-V-173

MIL-P-514

MIL-T-704MIL-F-3541MIL-C-3600

MIL-G-3859

MIL-G-10924MIL-B-1104OMIL-S–12514

MIL-c-13486

MIL-G-20241

MIL-G-23827

MIL-C-46168

MIL–S-81733

- Conduit Outlet Boxes, Bodies, andEntrance Caps, Electrical: CastMetal - for Shore Use.

- Motors, Alternating Current (Fractionaland Integral Horsepower, 500 HP andSmaller).

- Casters, Rigid and Swivel, Industrial,Heavy–Duty.

- Gages, Tire Pressure, Self-Contained andInflator-Gage, Pneumatic Tire.

- Conduit, Metal, Flexible.

- Varnish, Moisture-and-Fungus–Resistant (for Treatment of Communi-cations, Electronic, and AssociatedEquipment).

- Plate, Identification, Instruction andMarking, Blank.

- Treatment and Painting of Materiel.- Fittings, Lubrication.- Compressors, Rotary, Power-Driven;

and Compressors, Reciprocating, Power-Driven: Air and Gas (Except Oxygen

and Refrigerant), Packaging of.- Grease Guns, Hand-Operated, Lever,

Push and Screw Type.- Grease, Automotive and Artillery.- Belt, V: Drive.- Starters, Motor; Across-the-Line and

Reduced Voltage Types, A-C Induction,3/4 to 100 HP, Manual and Electric.

- Cable, Special Purpose, Electrical:

Low–Tension, Heavy Duty Single Con-ductor and Multiconductor.

– Gasket Material, Wool Felt, Impregnated,Adhesive, Pressure-Sensitive.

- Grease, Aircraft and Instrument, Gearand Actuator Screw.Coating, Aliphatic Polyurethane, ChemicalAgent Resistant.Sealing and Coating Compound, CorrosionInhibitive.

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STANDARDS

FEDERAL

FED-STD-H28

MILITARY

MIL-STD-130

MIL-STD-209

MIL-STD-838

MIL-STD-889

– Screw–Thread Standard for Federal Services.

- Identification Marking of US MilitaryProperty.

- Slinging and Tiedown Provisions forLifting and Tying Down Military Equip-ment.

- Lubrication of Military Equipment.

- Dissimilar Metals.

HANDBOOK

MILITARY

MIL-HDBK-113 - Guide for the Selection of Lubricants,Fluids, Preservatives and Speciality Pro-ducts for Use in Ground Equipment Systems.

(Copies of specifications, standards, and drawings required by contractors inconnection with specific acquisition functions should be obtained from thecontracting activity or as directed by the contracting officer.) .

2.2 Other publications. The following document(s) form a part of thisspecification to the extent specified herein. The issues of the documents whichare indicated as DoD adopted shall be the issue listed in the current DoDISS andthe supplement thereto, if applicable.

AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)

Boiler and Pressure Vessel Code, Section VIII.Performance Test Code 9 - Displacement Compressors, Vacuum Pumps andBlowers.

(Application for copies should be addressed to the American Society ofMechanical Engineers, 345 East 47th Street, New York, NY 10017.)

SOCIETY OF AUTOMOTIVE ENGINEERS (SAE)

SAE J492 - Rivets and Riveting.SAE J833 - USA Human Physical Dimensions, Recommended Practices.

(Application for copies should be addressed to the Society of AutomotiveEngineers, 400 Commonwealth Drive, Warrendale, PA 15096.)


MIL-C-13874J

NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION (NEMA)

ICS Enclosures for Industrial Controls and Systems.

(Application for copies should be addressed to the National ElectricalManufacturers Association, 155 East 44th Street, New york, NY 10017o)

AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)

B15.1 - Mechanical Power Transmission Apparatus, Safety Standard for.

(Application for copies should be addressed to the American National StandardsInstitute, Inc., 1430 Broadway, New York, NY 10018.)

SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT.

Rule 442 - Usage of Solvents.

(Application for copies should be addressed to the South Coast Air QualityManagement District, 9150 Flair Drive, El Monte, CA 91731)

UNDERWRITERS LABORATORIES (UL)

UL6 - Rigid Metal Conduit.UL514 - Nonmetallic Outlet Boxes, Flush Device Boxes, and Covers.UL1242 - Intermediate Metal Conduit.

(Applicationfor copies should be addressed to the Underwriters Laboratories, ●333 Pfingsten Road, Northbrook, IL 60062.)

(Industry association specifications and standards are generally available forreference from libraries. They are also distributed among technical groups and

using Federal agencies. )

2.3 Order of precedence. In the event of a conflict between the text of this

specification and the references cited herein, the text of this specification

shall take precedence.

3. REQUIREMENTS

3.1 Description. The air compressor shall be of the commercial classification“garage type” and shall consist of either an air-cooled, piston compressor unit

or air-oil cooled, rotary compressor unit, both types with an air reservoir,

airhose and power unit.

3.2 First article. The contractor shall furnish one or more compressorsfor examination and test within the time frame specified (see 6.2), to proveprior to starting production that his production methods and choice of designdetail will produce compressors that comply with the requirements of this


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specification. Examination and tests shall be as specified in section 4; and,

unless otherwise specified herein, all examination and tests shall be conductedby the contractor subject to surveillance and approval by the Government (see

6.3). When specified (see 6.2), the Government may conduct any or all of thefirst article examinations and tests, as specified (see 6.2).

3.3 Material. Material shall be as specified herein. Materials notspecified shall be selected by the contractor and shall be subject to allprovisions of this specification (see 6.9).

3.4 Material deterioration and control. The air compressor shall befabricated from compatible materials, inherently corrosion and deteriorationresistant or treated to provide protection against the various forms of

corrosion and deterioration that may be encountered in any of the applicablestorage and operating environments to which the air compressor may be exposed.

3.4.1 Dissimilar metals. Dissimilar metals, as defined in MIL–STD-889, shallbe electrically insulated from one another to minimize or prevent galvaniccorrosion. Insulation may be provided by an insulating barrier such as acorrosion inhibiting sealant conforming to MIL-S-81733 or chromate tapeconforming to MIL-G-20241. Protection against corrosion could also be obtainedby exclusion of the electrolyte if feasible.

3.4.2 Identification of materials and finishes. The contractor shall identifythe specific material, material finish or treatment for use with components and

sub-components, and shall make information available, upon request, to thecontracting officer or designated representative.

3.4.3 Recovered materials. For the purpose of this requirement, recoveredmaterials are those materials which have been collected from solid waste and

‘ reprocessed to become a source of raw materials, as distinguished from virginraw materials. The components, pieces and parts incorporated in the aircompressor may be newly fabricated from recovered materials to the maximumextent practicable, provided the air compressor produced meets all other

requirements of this specification. Used, rebuilt or remanufactured components,

pieces and parts shall not be incorporated in the air compressor.

3.5 Operating temperature. The compressors shall perform as specified herein

in any ambient temperature from 120° F to minus 25° F.

3.6 Safety and human factors.

3.6.1 Safety. All rotating or reciprocating parts and other parts subject tohigh operational temperatures that are of such a nature or are so “located as tobe a hazard to operating personnel, shall be guarded or insulated to the extent

necessary to eliminate the hazard. Protective devices shall not impair the

operating functions.

3.6.2 Human factors. The characteristics of the compressor shall provide for

operation by personnel ranging from the small man (5th percentile), through the

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large man (95th percentile), in accordance with SAE J833, including arcticclothed personnel.

3.7 Maintainability. The compressor shall operate as specified hereinwithout repair or maintenance other than the contractors recommended normalscheduled adjustments and servicing, as established by a maintenance scheduleprepared and submitted by the contractor prior to test. All major assembliesand installed attachments shall be accessible for maintenance repair andreplacement without removal of other major assemblies and installed attachments

not normally removed. Cover plates which must be removed for componentadjustment shall be equipped with quick-disconnect fastenings. All fastenersshall be of corrosion-resistant material or shall be treated to be corrosionresistant. All screw threads shall be in accordance with FED-STD-H28. Maximumuse shall be made of interchangeable hardware and fastening devices. Use ofself-tapping screws shall not be permitted. Means for drainage of lubricants,and condensate traps shall be in an accessible location and shall drain to acontainer without splashing on any component or on operating personnel. Thedrain outlets shall be so located to facilitate complete drainage. Eachmaintenance, assembly or disassembly operation performed as a result of testingshall be accomplished by not more than two men using common tools and specialtools furnished with the compressor.

3.8 Airhose. The airhose shall be the commercial heavy duty type 5/16 inchID, minimum working pressure shall be no less than 200 pounds per square inch

(psi) and unless otherwise specified (see 6.2) shall be not less than 50 feetlong. Air hose couplings shall be internal swivel fitted, having a l/4-inch,standard, straight-pipe thread and a 30-degree tapered seat and shall be fittedat one end with an inflator gage conforming to GG-G-91, type III.

3.9 Intake air filter and silencer. The compressors shall be provided with a

dry-type combination intake air filter and silencer.

3.10 Lubrication. All surfaces requiring lubrication shall be provided witha means for lubricating.

3.10.1 Lubricants. The compressors shall operate as specified herein whenlubricated with military lubricants (see 6.4).

3.10.2 Lubrication fittings. Lubrication fittings shall conform to MIL-F-3541,type 1, 11 or III. Fittings shall be located in protected positions. Fittings

shall be accessible to a grease gun conforming to MIL-G-3859, type II. Access-ibility to fittings shall be provided without the removal or adjustment ofaccessories or parts. Panels and plates equipped with hand–operable, quick–disconnect fasteners may be removed to provide accessibility to lubrication

fittings.

3.10.3 Pressure–release device. A pressure–release device shall be providedwhere the use of pressure lubricating equipment will damage grease seals orother parts.

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●3.10.4 Enclosures with integral reservoir of lubricant. Enclosures, such as

gear cases and transmission housings which contain a reservoir of lubricants forthe lubrication of the parts enclosed, shall be equipped with dipsticks, checkplugs not less than l/2-inch pipe size, or sight gages to determine the level ofthe lubricant. Each enclosure shall be equipped with a drainplug. Each enclosureshall be equipped with a means for filling the enclosure with lubricant. Thedrainplug shall be located so that removal of the drainplug will result incomplete drainage of the lubricant from the enclosure. Drainage shall be to acontainer when the compressor is in its normal position. Tubes maybe used to.convey the lubricant from the drain to a container. Accessibility to the drain-plug, the filling means, and the lubricant-level checking device shall beobtained without the removal or adjustment of accessories or parts. ~~

3.10.5 Delivery lubrication service. When delivered, all components, exceptthose for which preservatives are specified in 5.1, shall be lubricated. Greaselubrication, excluding lubrication of sealed bearings, shall be with greasesconforming to MIL-G-10924 or MIL-G-23827. Unless otherwise specified herein,all components shall be filled to the operating level with military oilsdesignated for use in the temperature range as specified herein. Eachlubricated component shall be tagged in a conspicuous place to indicate the

temperature range and grades of oils and greases used.

3.11 Fungus and moisture resistance. The electrical circuitry, including allcomponents and connections except as specified below, shall be protected fromthe effects of moisture and fungus growth by an overall treatment with a varnish

●conforming to MIL-V-173, composition I or II as applicable, 7 percent salicyl-anilide (by weight) based on the nonvolatile content of the varnish:

a. Components or circuit elements that are inherently fungus andmoisture resistant or which are hermetically sealed need not betreated.

b. Components or circuit elements whose functions will be adverselyaffected by the varnish coating shall not be treated.

When used, the varnish shall be applied by spray, brush, or a combination ofboth to give a minimum dry-film thickness of 1 mil to component or element

surfaces previously cleaned and prepared so that the surfaces are free from allforeign matter which would interfere with the adherence or function of the

varnish.

3.11.1 Composition. Composition II shall be used only in the case when localair pollution regulations in the application of varnish precludes the use of.composition I. When composition II is used, the contractor shall provi,de

evidence to the Government that the use of composition II is required, and shall

certify that composition 11 material complies with Rule 442 - Usage of Solvents.

3.12 Identification marking. The compressor shall be identified in accord-ance wtih MIL-STD-130. The marking shall be applied to the compressor onidentification plates conforming to MIL-P-514, type I, style 1, composition C,of type I, grade A, class 1 material. Plates, shall be attached by screws, bolts

or rivets in a conspicuous protected location.

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3.13 Instruction plates. Each compressor shall be equipped with instructionplates or diagrams, including warnings and cautions, describing any special or ●important procedures to be followed in assembling, operating or servicing thecompressor. Instruction plates shall conform to MIL-P-514, type III, compositionC, of type I, grade A, class 1 material. Plates shall be attached by screws,

bolts or rivets in a conspicuous protected location.

3.14 Treatment and painting. The compressor, components, and parts paintedin commercial Dractice shall be cleaned, treated and painted in accordance with.MIL-T-704, type F, or G as applicable. ‘Unless otherwise specified (see 6.2),top coat color shall be camouflage green 383 conforming to MIL–C-46168.

3.15 Type I, reciprocating.

3.15.1 Compressor. The type I compressor shall deliver the capacities of freeair (see 6.5) specified in table I at a pressure of 175 pounds per square inch

gage, (psig) as determined by the ASME Performance Test Code 9 - DisplacementCompressors, Vacuum Pumps, and Blowers. The components of the compressor shall

be balanced so that when the compressor is operated in conjunction with theelectric motor, vibration shall be minimized. The compressor shall produce

rated capacity at rated pressure for 500 hours in operating periods of not lessthan 4 hours. Operating periods of not less than 4 hours (see 4.6.2.4), duringhigh and low temperature tests may be counted (see 4.6.2.5 and 4.6.2.6). Thecompressor shall not exceed the contractors recommended continuous operatingspeed. The compressor shall be air cooled. The cylinder heads or cylinder

assembly (if cast integrally) shall be removable. The intake and exhaust valves

shall be removable. A fan shall be provided for cooling.

TABLE 1. Compressor characteristics.

Minimum Maximum Rated

capacity operating discharge

Size (free air) pressure pressure

(cfm)~ (Cfm) (psig) (psig)

5 5 200 175

15 15 200 175

~ 25 25 200 175

~ cfm – cubic feet per minute.

3.15.2 Intercooler and aftercooler. When a multiple-stage compressor is

furnished, an intercooler shall cool the air between the pressure stages andshall be located so as to be cooled by the airblast from the fan. Aspring–loaded-type, pressure–relief valve shall be installed between the

pressure stages to protect the low-pressure cylinder in case of failure of thehigh-pressure cylinder valves. The temperature measured at the discharge of theair receiver shall not exceed ambient plus 100” F at a pressure of 200 psig. If

necessary to meet the temperature requirements specified herein, an aftercoolermay be provided between the last stage of the compressor and the air receiver

tank. Aftercoolers shall be air cooled.

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3.15.3 Pressure tubing and fittings. All pressure tubing and fittings shallbe rated to withstand 1-1/2 times their normal working pressure.

3.15.4 Drive. The drive shall consist of matched multiple V-belts andgrooved pulleys on the power unit and compressor unit. All drive belts shallconform to MIL-B-1104O. A means for belt removal and adjustment shall beprovided.

3.16 Type 11, rotary.

3.16.1 Compressor. The type II compressor shall deliver the capacities offree air specified in table I at a pressure of 175 psig as determined by theASME Performance Test Code 9 - Displacement Compressors, Vacuum Pumps, andBlowers. The components of the compressor shall be balanced so that when thecompressor is operating in conjunction with the electric motor, vibration shallbe minimized. The compressor shall produce rated capacity at rated pressure for

500 hours in operating periods of not less than 4 hours (see 4.6.2.4). Oper-ating periods of not less than 4 hours during high and low temperature tests may

be counted (see 4.6.2.5 and 4.6.2.6). The compressor shall not exceed thecontractor’s recommended continuous operating speed. The compressor unit shallbe positive displacement and air cooled. A means shall be provided to removeand recover the oil from the discharge air. When a filter-type separator isused, it shall be accessible for examination, cleaning and replacement withoutremoval of other parts or components. To prevent hydraulic lock upon starting,a means shall be provided in the stator assembly to allow accumulated oil topass into the sump. The rotors, stators, and blades for any one size compressorshall be interchangeable among all compressors of that type, class and sizefurnished by that manufacturer. A pressure gage shall be provided between thecompressor unit and the separator discharge to indicate the pressure in thecompressor. A nonreturn valve shall be provided either in the oil separator or

in the discharge from the separator to prevent reverse flow of air from thereceiver.

3.16.2 Pressure tubing and fittings. All pressure tubing and fittings shallbe rated to withstand 1-1/2 times their normal working pressure.

3.16.3 Drive. The type II compressor shall be either direct drive ormultiple V-belt drive. The multiple V-belt drive shall conform to 3.15.4. Whena direct drive is used, a flexible coupling shall be installed between the powerunit and compressor unit. The mounting base for the power unit shall have ameans for belt removal and adjustment when V-belt drive is used.

3.17 Class 1, tank-mounted. The compressor unit and power unit shall be

mounted on a base attached to the air-receiver tank.

3.17.1 Air-receiver tank. The air-receiver tank for the class 1 compressorshall be of the horizontal type and shall be constructed in accordance with theASME Boiler and Pressure Vessel Code, Section VIII. The receiver shall bear the

ASME stamp and no welding or other actions shall be permitted after the receiverhas been certified. Unless otherwise specified (see 6.2), the capacity of the

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air-receiver tanks for the 5-cfm shall be not less than 20 gallons and for the15-cfm and 25-cfm compressors shall be not less than 80 gallons. Unless ●otherwise specified (see 6.2), the air-receiver tank fittings shall include a

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globe discharge valve, a drain cock and a O-psig to not less than 250-psigpressure gage having 10 psig or smaller increments. The air-receiver tanksshall include a pressure relief valve conforming to ASME Boiler and PressureVessel Code. The receiver shall be provided with a steel base of not less than

four mounting feet for horizontal mounting. When equipped with a steel base,openings shall be provided to permit insertion of forklift tines. Each openingshall be not less than 11 inches by 3 inches in size; openings shall be locatedsuch that the center of gravity of-the compressor falls between the centers offorklift openings. A means shall be provided on the receiver for securing the

airhose.

3.18 Class 3, caster-mounted. The compressor unit and power unit shall bemounted on a steel base attached to a horizontal-type, air-receiver tank. Theair-receiver shall be constructed as specified in 3.17, except the tank shall bemounted on four casters conforming to FF-C-88. Two type II (swivel) casters

shall be mounted on the compressor end, and two type I (nonswivel) casters shallbe mounted on the motor end.

3.18.1 Caster installation. The casters shall be mounted so that thecompressor will not overturn when pushed or pulled about on a horizontal surface

or when tilted 15 degrees from the horizontal in any direction. The castersshall be attached to steel mounts on the bottom side of the receiver tank andlocated near each end of the tank. The distance between the centerline of thecasters (measured side to side) shall be not less than 6 inches greater than themaximum diameter of the air-receiver tank. ●

3.18.2 Handle and storage rack. The class 3 compressor shall be equipped

with a combination handle and storage rack. The handle and storage rack shall

be removable, and similar to that shown on figure 1 (see 6.6). The handle shallbe positioned not less than 30 inches and not more than 40 inches from thefloor. The storage rack shall hold the airhose specified in 3.8 and 50 feet ofNo. 10 AWG, type SO, 3-conductor cable. The storage rack shall be located sothat neither hose nor cable, when stored on the rack, will contact any componentof the compressor subject to high temperatures.

3.18.3 Tilt requirement. The compressor shall deliver rated capacity whenoperated at rated speed and pressure, tilted 15 degrees from the horizontal in

any plane.

3.19 Class 4, base mounted. The compressor unit and power unit shall be

mounted on a base attached to a horizontal-type air-receiver tank. The air-receiver tank shall be constructed as specified in 3.17.

3.19.1 Toolbox. A toolbox made of No. 14 gage sheet steel shall be furnished

with the lid edges formed to overlap the top edges of the box to prevent theentry of dirt, snow, and rain. The toolbox shall be of sufficient size to holdthe canvas cover, all maintenance tools, inflator gage and publications.

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3.19.2 Lifting attachments. The base-mounted 15-cfm compressor shall beequipped with permanently affixed lifting attachments conforming to MIL-STD-209that will enable the compressor to be lifted in its normal travel position.

3.20 Electric-motors. Motor wiring and control systems shall conform to theprovisions of American National Standards Institute (ANSI) Standard B15.1.

3.20.1 Electric motor. Unless otherwise specified (see 6.2), each compressorshall be driven by a style AZ (dripproof) electric motor conforming to CC-M-1807.The electric motor shali have the ~ontinuous horsepower rating as ~pecified intable II. The horsepower required by the compressor when performing at 200 psigshall be not more than the continuous horsepower rating, including the servicefactor, of the motor. The motor shall have all electrical equipment connectedfor operating on a power supply having the characteristics as specified (see6.2).

TABLE II. Electric motor ratings.

Compressor size Minimum horsepower rating

(cfm) (hp)

5 2.015 5.025 10.0

3.20.2 Starter. A starter shall be furnished conforming to MIL-S-12514, typeI, class 2, and shall be provided with a NEMA type 12 (dripproof) and dust tight

enclosure. The class 2 starter shall be magnetically operated by a pressureswitch. The starter shall be reset by an externally operable switch mounted in

motor starter enclosure. The maintained contact stop-start switch and resetshall be located in an accessible location.

3.20.2.1 Low-voltage protection. A low-voltage protective device shall beprovided to open all ungrounded line conductors whenever voltage fails or drops

below a predetermined level or after the operation of the overload protectivedevice. After the operation of the overload protective device, the reset switch

shall require actuation before the motor can be restarted. The overload pro-tective device shall be removable and replaceable. The holding coil may beregarded as the low-voltage protective device. Certification shall be provided

demonstrating conformance to this requirement. Certification shall be madeavailable for review by the contracting officer or contracting officer’s represent-ative.

3.20.3 Conduit. Wiring shall be installed in conduit conforming to WW-C-566,UL6, UL514, or UL1242, as applicable. Conduit outlets shall conform to W-C-586.

3.20.4 Pressure regulation. Each compressor shall have an adjustable,

pressure-actuated electric control. The control shall be ad-justed to stop the

motor when the pressure has risen to 200 psig, plus O psig, minus 10 psig, and

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to start the motor when the pressure has dropped to 175 psig, plus or minus 10psig. A device shall be provided to protect the motor from starting againsttank pressure. ●

3.20.5 Electrical conductive casters. Class 3, compressor shall be providedwith electrical conductive casters.

3.20.6 Wiring. The cableaccordance with MIL-C-13486,

applicable. The wires shallstructural members.

for wiring the electrical system shall be inlow-temperature (minus 25° F), type and size as

be enclosed in a loom and clamped neatly to the

3.21 Pulley, 5–cfm Compressors. When a V-belt drive is used, the drivepulley shall be provided with an inner hub which clamps to the shaft by moving

axially along a taper in the outer hub. The mechanical clamping shall beaccomplished by the use of a screw member or members for mounting and removal of

the pulley.

3.22 Interchangeability. All parts having the same part number shall befunctionally and dimensionally interchangeable. Interchangeable parts aredefined as two or more parts possessing such functional and physical character-istics as to be equivalent in performance and durability and capable of beingexchanged one for the other without alteration of the parts themselves or ofadjoining parts, except for adjustment, and without selection for fit orperformance.

3.23 Workmanship. All parts, components and assemblies of the compressorincluding castings, forgings, molded parts, stampings, bearings, seals, machined ●surfaces, and welded parts shall be clean and free from sand, dirt, fins, pits,

sprues, scales, or any damaging extraneous material. The compressor shall befree of any defect that could impair its operation and serviceability.

3.23.1 Fabrication. Steel and aluminum used in the fabrication of thecompressors shall provide original quality surface finish and shall be free fromkinks and sharp bends. The forming of the material shall be done by methodsthat will not cause damage to the metal. Shearing and chipping shall be doneneatly and accurately. Corners shall be square and true, and sharp edges andburrs shall be removed. Flame-cutting may be employed instead of shearing andsawing. Burned surfaces of flame-cut material shall be ground or machinedsufficiently to remove ash and cooling checks. Precautions shall be taken toavoid overheating, and heated metals should be allowed to cool slowly. Al1

bends of a major character shall be made with metal dies or fixtures to insureuniformity of size and shape.

3.23.2 Welding. The surfaces of parts being welded shall be free of scale,

paint, grease, and other foreign matter. Welds shall transmit stress without

permanent deformation or failure when the parts connected by the welds aresubjected to proof and service loading.

3.23.3 Bolted connections. All boltholes shall be accurately punched or

drilled and shall have the burrs removed. Washers or lockwashers shall be

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● provided where necessary. All bolts, nuts, and screws shall be correctlytorqued and shall have full thread engagement. Matching thread areas securingbolts or capscrews shall be of sufficient strength to withstand the tensilestrength of the bolt.

3.23.4 Riveted connections. Rivets shall fill the holes completely. Theupset rivet heads shall be full, neatly made, concentric with the rivet holes,and in full contact with the surface of the member and shall be in accordancewith SAE J492.f

3.23.5 Machine work. Tolerancesthe limitations specified herein.

4. QUALITY ASSURANCE PROVISIONS

and gages for metal fits shall conform to

4.1 Responsibility for inspection. Unless otherwise specified in the‘contract, the contractor is responsible for the performance of all inspectionrequirements as specified herein. Except as otherwise specified in the‘contract, the contractor may use his own or any other facilities suitable for

the performance of the inspection requirements specified herein, unlessdisapproved by the Government. The Government reserves the right to’perform any

of the inspections set forth in the specification where such inspections aredeemed necessary to assure supplies and services conform to prescribed

requirements.

o 4.1.1 Component and material inspection. The contractor is responsible for

insuring that components and materials used are manufactured, examined andtested in accordance with referenced specifications and standards.

4.2 Classification of inspections. The inspection requirements specifiedherein are classified as follows:

a. First article inspection (see 4.3).b. Quality conformance inspection (see 4.4).c. Inspection comparison (see 4.7).

d. Inspection of packaging (see 4.8).

4.3 First article inspection.

4.3.1 Examination. The first article compressor shall be examined as

specified in 4.6.1. Presence of one or more defects shall be cause for

rejection.

4.3.2 Tests. The first article compressor shall be tested as specified in4.6.2.1 through 4.6.2.12 as applicable for the class compressor to be furnished.Failure of any test shall be cause for rejection. A first article test log (see

figure 2) shall be furnished.

4.4 Quality conformance inspection.

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4.4.1 Examination.4.6.1.

4.5 Tests.

MIL-C-13874J

Each compressor shall be examined in accordance with

4.5.1 Individual. Each compressor shall be Cested as specified in 4.6.2.12.Failure of a test shall be cause for rejection.

4.6 Inspection procedure.

4.6.1 Examination. The compressor shall be examined for the followingdefects:

Major

101.102.

1030104.

105.

106.107.108.109.110.111.

112.113.

114.115.

116.

117.118.119.120.121.122.123.124.125.126.127.128.129.130.131.

Material not as specified (see 3.3).Materials not resistant to corrosion and deterioration or treated

to be made resistant to corrosion and deterioration (see 3.4).Dissimilar metals not in accordance with MIL-STD-889 (see 3.4.1).Material and material finish or treatment information not available(see 3.4.2).Used, rebuilt or remanufactured components, pieces, or parts incor-porated in the compressor (see 3.4.3).Safety devices or guards missing or not as specified (see 3.6.1).Human factors not as specified (see 3.6.2).Maintainability not as specified (see 3.7).Airhose not as specified (see 3.8).Intake air filter and silencer not as specified (see 3.9).Lubrication not as specified (see 3.10).

Lubricants not as specified (see 3.10.1).Lubrication fittings not as specified (see 3.10.2).

Pressure-release device not as specified (see 3.10.3).Enclosures with integral reservoir of lubricant not as specified

(see 3.10.4).Delivery lubrication service not as specified (see 3.10.5).

Fungus and moisture resistance not as specified (see 3.11).

Composition not as specified (see 3.11.1).Identification marking not as specified (see 3.12).Instruction plates not as specified (see 3.13).Treatment and painting not as specified (see 3.14).Color not as specified (see 3.14).V-belts and pulleys not as specified (see 3.15.4 and 3.16.3).Handle and storage rack not as specified (see 3.18.2).Toolbox not as specified (see 3.19.1).Base-mounted compressor not as specified (see 3.19).Electric motor not as specified (see 3.20.1).Starter not as specified (see 3.20.2).Low-voltage protection not as specified (see 3.20.2.1).Conduit not as specified (see 3.20.3).Wiring not as specified (see 3.20.6).

.

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MIL-C-13874J

132.133.

134.135.136.

137.138.139.140.

Pulley, 5-cfm compressors not as specified (see 3.21).Interchangeability not as specified (see 3.22).Workmanship not as specified (see 3.23).Fabrication not as specified (see 3.23.1).Welding not as specified (see 3.23.2).

Bolted connections not as specified (see 3.23.3).Riveted connections not as specified (see 3.23.4).Machine work not as specified (see 3.23.5).Electrical conductive casters not as specified (see 3.20.5’).

4.6.2.4 Endurance. ODerate the compressor for not less.continually in periods of not less than 4 hours of runningand other preventive maintenance shall be performed duringshall be no replacement of parts. Adjustments provided by

repairs which require 1 man-hour or less may be made. The

4.6.2 Tests.

4.6.2.1 Test conditions. The compressor shall operate as specified hereinwithout maintenance other than the contractor’s recommended normal scheduled

maintenance as established by a maintenance schedule prepared and submitted bythe contractor prior to test. The compressor shall be lubricated with military

oils and greases. A first article test log similar to figure 2 shall befurnished tabulating all appropriate test data and observations. Safety.andhuman factor considerations shall be evaluated throughout testing.

4.6.2.2 Air-receiver tank. The air-receiver tank for the compressor shall betested in accordance with the ASME Boiler and Pressure Vessel Code, SectionVIII. Failure of any ASME tests shall constitute failure of this test.

Presence of the ASME official code U-symbol stamped or marked on the receiverand the furnishing of a copy of the ASME data sheet (Form U-1) may be acceptedas evidence that the receiver conforms to the ASME Boiler and Pressure Vessel

Code.

4.6.2.3 Capacity and performance. The compressor capacity shall bedetermined in accordance with the method specified in the ASME Performance Test

Code 9 - Displacement Compressors, Vacuum Pumps, and Blowers. This test shallbe perfozmed in conjunction with and simultaneously with the endurance test (see

4.6.2.4). The air-discharge temperature shall be determined when the compressoris operating at minimum capacity at maximum discharge pressure. Any one of thefollowing conditions shall constitute failure of th:istest:

a. Discharge air pressure less than 175 psig.

b. Discharge air temperature in excess of ambient plus 100° F.c. Free-air capacity less than that specified in table II.

4.6.2.3.1 Power consumption. Test unit at rated speed and while delivering

its rated capacity for power consumption, using a calibrated motor or dynamom-

eter. Horsepower in excess of the continuous horsepower rating of the motorshall constitute failure of this test.

than 500 hourstime. Oil changesdowntime. Thereintegral devices and

500 hours of operation

15

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MIL-C-l3874J

shall be accomplished at rated capacity and pressure. Record appropriateremarks, including a record of all stops and adjustments. Record the following ●data at least once during each 24 hour period. Readings shall be taken onlyafter at least 1 hour of continuous operation:

a.b.c.d.e.f.

g“h.i..

:.1.

Air temperature, ambient.Air temperature at receiver discharge.Air receiver pressure.Barometric pressure.Air temperature at compressor intake.

Air temperature upstream of nozzle.Air pressure at compressor intake.Nozzle throat diameter.Nozzle coefficient of discharge.

Differential pressure across the nozzle.Compressor unit speed (rpm).Compressor capacity (cfm) computed.

Completion of less than 500 hours of operation at rated capacity and pressure,

discharge air temperature in excess of ambient plus 100° F, requirement forreplacement of parts, requirement for repairs requiring more than 1 man-hour tocomplete, or necessity for adjustment not provided for by integral devices shallconstitute failure of this test. Computed CFM capacity less than specified

shall constitute failure of this test (see 3.15.1 and 3.16.1).

4.6.2.5 High temperature. Unless otherwise specified, subject the compressorto an ambient temperature of 120° F plus or minus 5° F until all components have ●stabilized at this temperature in the test chamber. Then start and operate thecompressor at rated capacity and pressure for not less than 4 hours whilemaintaining 120° F plus or minus 5° F ambient temperature. The operating timefor this test may be counted toward the accomplishment of the endurance test.Record the data as specified in 4.6.2.4 at 30-minute intervals. Failure to

start and operate at rated capacity, pressure and speed, discharge air tempera-ture in excess of ambient plus 100° F or requirement for replacement of parts

shall constitute failure of this test.

4.6.2.6 Low temperature. Unless otherwise specified, subject the compressor

to an ambient temperature of minus 25° F plus or minus 5° F until all components

have stablized at this temperature in the test chamber. Then start and operate

the compressor at rated capacity, pressure and speed for not less than 4 hours

while maintaining minus 25° F plus or minus 5° F ambient temperature. meoperating time for this test may be counted toward the accomplishment of theendurance test. Record the data as specified in 4.6.2.4 at 30-minute intervals.Failure to start and operate at rated capacity, pressure and speed, or

requirement for replacement of parts shall constitute failure of this test.

4.6.2.7 Cycling. Start the compressor and allow the receiver pressure tobuild up until the pressure-regulation control operates. Then reduce the

receiver pressure until the pressure-regulation control activates to increasethe pressure. Vary the pressure as above until a total of 20 high-pressureactuations and 20 low-pressure actuations have been reached. Inability of the

16


MIL-C-13874J

●pressure-regulation control to control the pressure as specified shall constitutefailure of this test.

r.

4.6.2.8 Pressure regulation. When an adjustable pressure-regulating valve ofthe pressure-relief type actuated by receiver pressure is used at the beginningand after completion of the endurance test, start the compressor and allow thereceiver pressure to build up to determine pressure required to discharge fullcapacity through the pressure-regulating valve. Then reduce the receiver pres-sure to determine the pressure at which the pressure-regulating valve reseats.

Inability to meet the requirements specified in 3.20.4 shall constitute failureof this test.

4.6.2.9 Class 3.

4.6.2.9.1 Casters. Push and pull the compressor horizontally in all direc-tions, turn the compressor 360 degrees, and tilt the compressor 15 degrees fromthe horizontal in all directions. Overturning or any condition that interfereswith the maneuverability of the compressor or physical damage to the compressor

shall constitute failure of this test.

4.6.2.10 Tilted operation. Tilt the compressor 15 degrees from the horizontalabout the longitudinal axis and operate in this position for 30 minutes. Thistest shall be performed in each of the four directions (compressor tilted withrespect to longitudinal and transverse axes). Allow the compressor to stand for

4 hours in the tilted position most likely to adversely affect the ‘lubrication

o then start and operate the compressor for 30 minutes in that position. Anymalfunction due to tilted operation such as lack of lubrication, rough orerratic operation, or permanent deformation of any part or component shallconstitute failure of this test.

4.6.2.11 Class 4.

4.6.2.11.1 Lifting attachment. Lift class 4, size 15-cfm compressor in itsnormal travel position using only the permanently affixed lifting attachments.

Determine the force and angle of application for each attachment and theclearance between each sling and the compressor. Then anchor the compressor and

subject each attachment to a load equal to 2-1/2 times the load determined aboveand applied at the angle determined above. Apply each load for not less than 90

seconds. Weld failure or permanent deformation of the lifting attachments orstructural members shall constitute failure of this test.

4.6.2.12 Capacity. Test each compressor for capacity in accordance with4.6.2.3 except that each compressor shall be tested as a unit driven by itselectric motor. Prior to testing, run-in each compressor as prescribed by the

contractor. Occurrence of one or more of the following conditions shall

constitute failure of this test:

a. Discharge air pressure less than 200 psig.b. Discharge air temperature in excess of ambient temperature plus

100° F.c. Free-air capacity less than that specified in table I.

—

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MIL-C-13874J

4.7 Inspection comparison. The Government may select compressors at any timeduring the contract production period and subject these compressors to theexamination specified in 4.6.1 and the tests specified to determine conformanceto the requirements of this specification. The inspection will be performed by

the Government, at a site selected by the Government, on units selected atrandom from those which have been accepted by the Government and will notinclude the previously inspected first article compressors. In addition to anytest specified as part of the inspection comparison, the Government reserves the

right to conduct any and all other tests contained in’this specification as partof the inspection comparison, and failure of such additional tests shall havethe same effect as failure of those tests specified as inspection comparison.

4.7.1 Inspection failure. Failure of an inspection comparison compressor tomeet any requirement specified herein during and as a result of the examinationand tests specified in 4.7 shall be cause for rejection of the inspectioncomparison compressor(s) and shall be cause for refusal by the Government tocontinue acceptance of production compressors until evidence has been providedby the contractor that corrective action has been taken to eliminate thedeficiencies. Correction of such deficiencies shall be accomplished by the

contractor at no cost to the Government on compressors previously accepted andproduced under the contract. Any deficiencies found as a result of the inspec–tion comparison will be considered prima facie evidence that all compressorsaccepted prior to the completion of inspection comparison are similarlydeficient unless evidence to the contrary is furnished by the contractor andsuch evidence is acceptable to the contracting officer.

4.8 Inspection of packaging. The preservation, packing, and marking shall be

examined and tested to determine compliance with the quality assurance provi-sions of MIL-C–3600.

5. PACKAGING

5.1 Preservation, packing, and marking. The air compressors, accessories,

repair parts, tools, and publications shall be preserved, packed, and marked inaccordance with MIL-C–3600. The level of preservation and the level of packingshall be level A, B or commercial as specified (see 6.2).

6. NOTES

6.1 Intended use. The compressors are intended for use as a source of

compressed air in the normal operations conducted at filling stations andvehicle maintenance shops.

6.2 Ordering data. Procurement documents should specify the following:

a. Title, number, and date of this specification.b. Type, class, and size required (see 1.2).c. Time frame required for submission of first article model and

number of compressors to be furnished (see 3.2).

18


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II

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MIL-C-13874J

d. When the Government will conduct any or all of the first articleexamination and tests. When the Government will conduct some but notall of the first article examination and tests, the contractingofficer should specify which examination and tests’will be conductedby the Government and which examination and tests shall be conductedby the contractor (see 3.2).

e. Length of airhose to be furnished if other than as specified (see 3.8).f. Color required (see 3.14).. Capacity of air-receiver tank if other than as specified (see 3.17.1).

:. Air-receiver tank fittings required if other than as specified (see

3.17.1).i. Style of motor if other than that specified in 3.20.1.

j= Power supply on which electric motors will operate (see 3.20.1).

(Dual-voltage motors may be furnished but only one of the voltagesshall be specified for the motor on the compressor).

k. Degree of preservation and packing required (see 5.1).

6.3 First article inspection. When a first article inspection is required,the items should be a preproduction model. The first article should consist ofone or more units. The contracting officer should include specific instructionsin acquisition documents regarding arrangements for examinations, tests andapproval of the first article test results and disposition of the document’sfirst article.

6.3.1 First article. Any changes or deviations of production compressorsfrom the approved first article model during production will be subject to theapproval of the contracting officer. Approval of the first article model will

not relieve the contractor of his obligation to furni:;hcompressors conformingto this specification. The contractor should provide a written report to thecontracting officer covering all deficiencies, malfunctions, and test failures.This report shall be presented within 48 hours from the time of failure andshould describe components and parts affected, both directly and indirectly;corrective action taken or to be taken by the contracf:or, and the contractor’s

proposed method of proving the adequacy of the corrective action.

6.4 Lubricants. Selection of lubricants, fluids, and greases shall be inaccordance with section 5 of MIL-STD-838. Unless otherwise authorized by the USArmy Belvoir Research and Development Center, lubricants, fluids and greases forground equipment systems shall be restricted to those listed under chapter 2 ofMIL-HDBK-113 .

6.5 Free air. Free air is defined as air at”atmospheric conditionssurrounding the compressor, at the point where the compressor is installed, butnot in the immediate vicinity where it may be affected by the heat of thecompressor.

6.6 Information figures. Figure 1 shows a caster-mounted compressor, whichhas been found acceptable; however, the figure is included for illustration onlyand is not intended to preclude the furnishing of other designs which conform to

this specification.

19


MIL–c-13874J

6.7 Data requirements. The contracting officer should include requirementsfor such data as technical publications, instructionalmaterials, illustratedparts lists, and contractor-’smaintenance and operation manual to be furnishedwith each compressor.

6.8 Provisioning. The contracting officer should include provisioningrequirements for repair parts and maintenance tools as necessary (including anyspecial tools), and instructions on shipment of compressors. A suggested

paragraph is as follows:

“Shipment of compressors shall include repair parts, maintenancetools, operational instructions,and accessories, unless exceptionsare provided elsewhere in the contract.”

6.9 Recycled material. It is encouraged that recycled material be used whenpractical as long as it meets the requirements of the specification (see 3.3).

Custodians: Preparing activity:Army - ME Army - ME

Navy - YDProject 4310-0168

Review activity:DLA–CS

User activity:Navy - MC

20


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mil-c-13874j 17 july 1985 superseding military...

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